In recent years there has been an increasing emphasis on the use of lightweight composite materials. One application, for example, has been their use to improve the efficiency of motor vehicles. To that end, the United States Government and the U.S. Council for Automotive Research (USCAR)—which represents Daimler Chrysler, Ford, and General Motors have partnered to form the Partnership for a New Generation of Vehicles (PNGV). One goal of PNGV is to develop technology, such as composite technology, that can be used to create environmentally friendly vehicles with up to triple the fuel efficiency, while providing today's affordability, performance and safety. For example, PNGV wants to improve the fuel efficiency of today's vehicles from about 28 miles per gallon (mpg) to about 83 mpg and a 40-60% decrease in the present curb weight (3200 pounds).
One method to improve the fuel efficiency is to decrease the weight of today's vehicles and use lighter weight materials. The materials used in today's vehicles, such as steel and aluminum, are quite heavy relative to composite materials, but have been necessary to provide sufficient structural properties, including tensile, compression, flexural, interlaminar shear, and in-plane shear strengths and other mechanical and material properties, to meet vehicle design requirements.
Many other applications of lightweight composites have been made to supplement or replace the use of structural materials, such as steel, cast iron, and aluminum. These include buildings, bridges, recreational vehicles, aerospace, defense, and sporting goods, as well as many other applications.
One way to increase the structural properties of materials, particularly the torsional or flexural strength, is to make them in a more structurally efficient form. In one structurally efficient form, metals like aluminum and steel have been combined with a supporting structure, such as a honeycomb core material, by sandwiching the honeycomb between panels of the metal. Examples of such combinations have been described in U.S. Pat. Nos. 4,291,205, 5,140,913, 5,192,623, 5,635,306, 5,875,596, and 5,899,037, the disclosures of which are incorporated herein by reference. In another structurally efficient form, composite materials have been combined with a supporting structure, such as a honeycomb or foam structure, by sandwiching the supporting structure between panels of the composite material. Examples of such combinations have been described in U.S. Pat. Nos. 5,006,391, 5,195,779, 5,652,039, 5,834,082, 5,848,767, 5,849,122, and 5,875,609, the disclosures of which are incorporated herein by reference.
Such combinations, however, have been generally limited to relatively flat structures and so applications of such materials have been quite limited. As well, the structural members have not contained additional components or elements that would enhance their use for applications other than just solely as structural members.